Formation of Nanocrystalline Silicon Carbide Powder from Chlorine-Containing Polycarbosilane Precursors

Nanocrystalline ß-SiC particulates with a grain-size range of 5-20 nm were prepared by heating a prepyrolyzed, chlorine-containing polysilane/polycarbosilane (PS/PCS) to 1600°C. The transformation from the prepyrolyzed PS/PCS to nanocrystalline SiC was investigated by differential thermal analysis, thermogravimetric analysis, X-ray diffractometry, mass spectrometry, and infrared spectroscopy. The results indicated that the nanocrystalline ß-SiC was formed by the crystallization of the PS/PCS random network and the crosslinking of Si-Si, Si-Cl, and Si-CH₂-Si bonds. Transmission electron microscopy observation showed that SiC particulates consisted of equiaxed, randomly oriented, ultrafine grains.